The invention relates to an ultrasonic array comprising an arrangement of transducer elements in rows and columns, wherein the transducer elements each have electrical contact means at opposite contact surfaces thereof, and wherein switches associated with the electrical contact means are operable to activate selected ones of the transducer elements to establish preselectable transmitting and/or receiving surfaces during a transmitting/receiving cycle, particularly for the purpose of dynamic focusing.
Ultrasonic arrays having the possibility of switchover for establishing transmitting surfaces and/or receiving surfaces are, for example, known in the case of an individual line array of optically switched transducer elements from the German Pat. No. 24 43 686, and in the case of a multiline-array (with shift register selected columns of transducer elements) from the German Auslegeschrift No. 26 34 918. In such arrays, switches are interposed between the transmit/receive circuitry and one set of contact surfaces while the other set of contact surfaces are connected to a common return path e.g. at ground potential. Also the type of transistor circuit used for switching permits only two states - connection or disconnection of the individual transducer elements in establishing a desired transmitting and/or receiving surface. A continuously variable degree of coupling of the individual elements with the object of producing a continuously variable aperture is not provided; and an introduction of continuously variable switching elements in the prior art systems would lead to an excessively high technical expenditure in view of the number of switches required in such systems.